Circuit arrangement for starting and operating a gas- and/or vapor discharge lamp

Abstract

A circuit arrangement for starting and operating a discharge lamp by means of an electronic ballast includes a series arrangement of a PTC resistor and an ohmic resistor connected in parallel with an electronic switch of the ballast, with only the PTC resistor being in parallel with a control circuit of the electronic switch. The value of the ohmic resistor is 8 to 12 times the cold resistance of the PTC resistor.

What is claimed is: 
     
       1. A circuit arrangement for starting and operating an electric discharge lamp including preheatable electrodes having free ends that are--at least during starting of the lamp--electrically interconnected, means connecting the lamp in series-connection with an electric ballast 
     
     
       2. Apparatus for energizing an electric discharge lamp having preheatable electrodes comprising, a pair of input terminals for connection to a source of supply voltage, an electronic controlled switch having a control electrode, means connecting said lamp in series with said electronic switch across said input terminals so that the electronic switch operates as an electric ballast to limit the lamp current, a control circuit coupled to the control electrode of the electronic switch for controlling the switch operation, a positive temperature coefficient (PTC) resistor, a first resistor having a resistance value greater than the cold resistance value of the PTC resistor, means connecting the first resistor and the PTC resistor in a series circuit, and means connecting said series circuit in shunt with the electronic switch and with the PTC resistor only in parallel with the control circuit whereby the electronic switch is maintained in a cut-off condition by the PTC resistor prior to ignition of the lamp. 
     
     
       3. Apparatus as claimed in claim 2 wherein the control circuit is connected to a junction point between the first resistor and the PTC resistor. 
     
     
       4. Apparatus as claimed in claims 2 or 3 further comprising an inductor and a capacitor coupled to said input terminals so as to form a low-pass filter for said apparatus. 
     
     
       5. Apparatus as claimed in claims 2 or 3 further comprising an inductor, a capacitor and a diode all connected in parallel with one another and in series with the lamp and the electronic switch and with the diode poled opposite to the electronic switch. 
     
     
       6. Apparatus as claimed in claims 2 or 3 wherein the resistance of the first resistor is 8 to 12 times the cold resistance of the PTC resistor. 
     
     
       7. Apparatus as claimed in claims 2 or 3 further comprising an inductor connected in parallel with the lamp. 
     
     
       8. Apparatus as claimed in claim 2 wherein the control circuit includes a capacitor that draws a charge current separate from the current flow in the PTC resistor. 
     
     
       9. Apparatus for energizing an electric discharge lamp having preheatable electrodes comprising, a pair of input terminals for connection to a source of AC supply voltage, an electronic controlled switch having a control electrode, means connecting said lamp in series with said electronic switch across said input terminals so that the electronic switch operates as an electric ballast to limit the lamp current, a control circuit coupled to the control electrode of the electronic switch for triggering the switch into operation at a frequency substantially higher than the supply voltage frequency, means coupled to the preheatable electrodes for providing a current path from the input terminals through the electrodes during the lamp pre-ignition period, and means coupled to the control circuit and to the input terminals for limiting the control circuit voltage during the lamp pre-ignition period to a value below the trigger voltage of the electronic switch thereby to hold the electronic switch in a cut-off condition for a time period sufficient to heat the preheatable electrodes to operating temperature.